might be spoken "start Spanish _Esta pagina en espanol_ end Spanish".
Refer also to information on matching attributes and attribute values
useful for language matching in CSS 2 ([CSS2], section 5.8.1).
If users don't want to see or hear blocks of content in another
language, allow the user to suggest hiding that content (e.g.,
with style sheets).
+ Implement content negotiation so that users may specify
language preferences. Or allow the user to choose a resource
when several are available in different languages.
+ Use an appropriate glyph set when rendering visually.
+ Use an appropriate voice set when rendering as speech.
+ Render characters with the appropriate directionality. Refer
to the "dir" attribute and the BDO element in HTML 4.0
([HTML40], sections 8.2 and 8.2.4 respectively). Refer also
to the Unicode standard [UNICODE].
+ A user agent may not be able to render all characters in a
document meaningfully, for instance, because the user agent
lacks a suitable font, a character has a value that may not
be expressed in the user agent's internal character encoding,
etc. In this case, section 5.4 of HTML 4.0 [HTML40]
recommends the following for undisplayable characters:
1. Adopt a clearly visible (or audible), but unobtrusive
mechanism to alert the user of missing resources.
2. If missing characters are presented using their numeric
representation, use the hexadecimal (not decimal) form
since this is the form used in character set standards.
+ Refer to "Character Model for the World Wide Web" [CHARMOD],
which defines various aspects of a character model for the
World Wide Web. It contains basic definitions and models,
specifications to be used by other specifications or directly
by implementations, and explanatory material. In particular,
early uniform normalization, string identity matching, string
indexing, and conventions for URIs are addressed.
__________________________________________________________
2.3 Provide time-independent access to time-dependent active elements
or allow the user to control the timing of changes.
[Priority 1]
Techniques:
+ Render time-dependent links instead as a static list that
occupies the same screen real estate. Include (temporal)
context in the list of links. For example, provide the time
at which the link appeared along with a way to easily jump to
that portion of the presentation.
+ Provide easy-to-use controls (including both mouse and
keyboard commands) to allow viewers to pause the presentation
and advance and rewind by small and large time increments.
+ Allow the user to navigate sequences of related links that
vary over time.
+ Provide a mode in which all active elements are highlighted
in some way and can be navigated sequentially. For example,
use a status bar to indicate the presence of active elements
and allow the user to navigate among them with the keyboard
or mouse to identify each element when the presentation is
moving and when it is paused.
+ Allow the user to to stop and start the flow of changes to
content. Prompt the user for confirmation of a pending
change.
__________________________________________________________
2.4 When no text equivalent has been supplied, indicate what type of
object is present. [Priority 2]
Techniques:
+ If no captioning information is available and captioning is
turned on, render "no captioning information available" in
the captioning region of the viewport.
+ The "Altifier Tool" [ALTIFIER] illustrates smart techniques
for generating text equivalents for images, etc. when the
author hasn't supplied any.
+ Use values of other known attributes that might give clues
about the object.
+ Refer to the section on frame techniques.
+ Refer to the section on link techniques.
__________________________________________________________
2.5 When a text equivalent for content is explicitly empty (i.e., an
empty string), render nothing. [Priority 3]
Checkpoints for user interface accessibility:
2.6 If more than one alternative equivalent is available for content,
allow the user to choose from among the alternatives. This
includes the choice of viewing no alternatives. [Priority 1]
For example, if a multimedia presentation has several tracks of
captions (or subtitles) available (e.g., in different
languages, different levels of detail, different reading
levels, etc.) allow the user to choose from among them.
Techniques:
+ Distinguish image links from their long descriptions
("longdesc" in HTML).
+ Allow users to received long description text, according to
their preference:
1. always
2. on request, with a brief signal should indicate its
presence (e.g. a tone)
3. on request, but without even that signal.
+ Make information available with different levels of detail.
For example, for a voice-activated browser, offer two options
for alternative equivalents to HTML images:
1. Speak only "alt" text by default, but allow the user to
hear "longdesc" text on an image by image basis.
2. Speak "alt" text and "longdesc" for all images.
+ Provide an interface which displays all available tracks,
with as much identifying information as the author has
provided, and allow users to choose which tracks are
rendered. For example, if the author has provided "alt" or
"title" for various tracks, use that information to construct
the list of tracks.
+ Provide an interface which allows users to indicate their
preferred language separately for each kind of equivalent.
The selection can be based on user preferences in either the
user agent (cf., the Content-Language entity-header field of
RFC 2616 [RFC2616], section 14.12) or the operating system.
Users with disabilities may need to choose the language they
are most familiar with in order to understand a presentation
which may not include all equivalent tracks in all desired
languages. In addition, international users may prefer to
hear the program audio in its original language while reading
captions in their first language, fulfilling the function of
subtitles or to improve foreign language comprehension. In
classrooms, teachers may wish to control the language of
various multimedia elements to achieve specific educational
goals.
The following image illustrates how users select preferred
language for captions in the Real Player.
Illustration of how user selects preferred language for
captions in Real Player
The next image illustrates how users select preferred
language in the Windows operating system under properties for
Regional Settings. This preference could be inherited by the
user agent.
Illustration of how user selects preferred language in the
Windows operating system
__________________________________________________________
2.7 Allow the user to specify that captions and auditory descriptions
be rendered at the same time as the associated auditory and
visual tracks. [Priority 1]
Note. Respect synchronization cues during rendering.
Techniques:
It is important that captions and auditory descriptions be
rendered synchronously with the primary content. This ensures
that users with disabilities can use the primary and equivalent
content in combination. For example, if a hard-of- hearing user
is watching a video and reading captions, it is important for
the captions to be synchronized with the audio so that the
viewer can use any residual hearing. For audio description, it
is crucial that the primary audio track and the auditory
description track be kept in sync to avoid having them both
play at once, which would reduce the clarity of the
presentation.
User agents that play SMIL ([SMIL]) presentations should take
advantage of a variety of access features defined in SMIL
(refer to "Accessibility Features of SMIL" [SMIL-ACCESS]). A
future version of SMIL (known currently as SMIL "Boston") is in
development and additional access features may be available
when this specification becomes a W3C Recommendation.
As defined in SMIL 1.0, SMIL players should allow users to turn
captions on and off by implementing the test attribute
system-captions which takes the values "on" and "off." For
example, include in the player preferences a way for users to
indicate that they wish to view captions, when available. SMIL
files with captions available should use the following syntax:
In this case, when the user has requested captions, this
textstream should be rendered, and when they have not it should
not be rendered.
SMIL 1.0 does not provide a test attribute to control auditory
descriptions. However, future versions of SMIL (including SMIL
"Boston") are expected to include such a test attribute. Should
SMIL "Boston" become a W3C Recommendation, developers should
implement it then. A test attribute to turn auditory
descriptions on and off should be implemented in parallel to
the implementation of the 'system-captions' attribute. Users
should be able to indicate the preference to receive auditory
description, when content authors make it available, through
the standard preferences setting section of user interface.
Another test attribute, 'system-overdub-or-captions' in SMIL
1.0, allows the user to choose between alternate language text
or sound. This attribute specifies whether subtitles or overdub
should be rendered for people who are watching a presentation
where the audio may be in a language they do not understand
fluently. This attribute can have two values: "overdub", which
selects for substitution of one voice track for another, and
"subtitle", which means that the user prefers the display of
subtitles. However, this attribute should not be used to
determine if users need captions. When both are available, deaf
users will prefer to view captions, which contain additional
information on music, sound effects, and who is speaking, which
are not included in subtitles since those are intended for
hearing people.
User agents that play QuickTime movies should provide the user
with a way to turn on and off the different tracks embedded in
the movie. Authors may use these alternate tracks to provide
alternative equivalents for use by viewers with disabilities.
The Apple QuickTime player currently provides this feature
through the menu item "Enable Tracks."
User agents that play Microsoft Windows Media Object
presentations should provide support for Synchronized
Accessible Media Interchange (SAMI), a protocol for creating
and displaying caption text synchronized with a multimedia
presentation. Users should be given a way to indicate their
preference for viewing captions. In addition, user agents which
play Microsoft Windows Media Object presentations should enable
viewers to turn on and off other alternative equivalents,
including auditory description and alternate visual tracks.
Other video or animation formats should incorporate similar
features. At a minimum, users who are blind and users who are
deaf need to be able to turn on and off auditory description
and and captions. The interface to set these preferences must
be accessible. Information on how to author accessible tracks
should be included in documentation about the media player.
__________________________________________________________
2.8 If a technology allows for more than one audio track, allow the
user to choose from among tracks. [Priority 1]
Techniques:
+ Refer to techniques for [#choose-equivalent].
+ Make apparent through the user interface which tracks are
meant to be played mutually exclusively.
__________________________________________________________
2.9 For identified but unsupported natural languages, allow the user
to request notification of language changes. [Priority 3]
Note. The user should be able to request no notification of
language changes.
Techniques:
A user agent should treat content language as part of
contextual information. When the language changes, the user
agent should either render the content in the supported
language or notify the user of the language change (if
configured for notification). Rendering could involve speaking
in the designated language in the case of an audio browser or
screen reader. If the language was not supported, the language
change notification could be spoken in the default language by
a screen reader or audio browser.
Language switching for blocks of content may be more helpful
than inline language switching. In some language combinations,
less than a few words long foreign phrases are often
well-integrated in the primary language (e.g., Japanese being
the primary and English being the secondary or quoted). In such
situations, dynamic switching in in-line level may make the
reading sound unnatural, and possibly harder to be understood.
Language information for HTML ("lang", "dir") and the
Extensible Markup Language (XML) ("xml:lang") should be made
available through the Document Object Model (DOM) ([DOM1],
[DOM2]).
User agents may announce language changes using style sheets to
generate text (refer to CSS 2 [CSS2] and XSLT [XSLT]) that
indicates the change of language.
__________________________________________________________
Guideline 3. Allow the user to turn off inaccessible features
In addition to the techniques below, refer also to the section on user
control of style.
Checkpoints for content accessibility:
3.1 Allow the user to turn on and off rendering of background images.
[Priority 1]
Techniques:
+ Allow the user to turn off embedded or background images
through the user interface. Note that any alternative
equivalents for those images must still be available.
+ In CSS background images may be turned on/off with the
'background' and 'background-image' properties ([CSS2],
section 14.2.1).
__________________________________________________________
3.2 Allow the user to turn on and off rendering of background audio.
[Priority 1]
Techniques:
+ Allow the user to turn off background audio through the user
interface.
+ Users sometimes specify background sounds with the "bgsound"
attribute. Note. This attribute is not part of HTML 4.0
[HTML40].
+ In CSS 2, background sounds may be turned on/off with the
'play-during' property ([CSS2], section 19.6).
__________________________________________________________
3.3 Allow the user to turn on and off rendering of video. [Priority 1]
Techniques:
+ Allow the user to turn off video through the user interface.
Render a still image in its place.
+ Support the 'display' property in CSS.
__________________________________________________________
3.4 When the user agent renders audio natively, allow the user to turn
on and off rendering of audio. [Priority 1]
Note. To render audio natively means that the user agent drives
the speaker directly.
Techniques:
+ Allow the user to turn off audio through the user interface.
+ Support the CSS 2 'display', 'play-during', and 'speak'
properties in ([CSS2], sections 9.2.5, 19.6, and 19.5,
respectively).
__________________________________________________________
3.5 Allow the user to turn on and off animated or blinking text.
[Priority 1]
Techniques:
+ Allow the user to turn off animated or blinking text through
the user interface (e.g., by hitting the ESCAPE key to stop
animations). Render static text in place of blinking text.
+ The BLINK element. Note. The BLINK element is not defined by
a W3C specification.
+ The MARQUEE element. Note. The MARQUEE element is not defined
by a W3C specification.
+ The CSS 'blink' value of the 'text-decoration' property.
__________________________________________________________
3.6 Allow the user to turn on and off animations and blinking images.
[Priority 1]
Techniques:
+ Allow the user to turn off animated or blinking text through
the user interface (e.g., by hitting the ESCAPE key to stop
animations). Render a still image in its place.x
__________________________________________________________
3.7 Allow the user to turn on and off support for scripts and applets.
[Priority 1]
Note. This is particularly important for scripts that cause the
screen to flicker, since people with photosensitive epilepsy
can have seizures triggered by flickering or flashing
particularly in the 4 to 59 flashes per second (Hertz) range.
Techniques:
Peak sensitivity to flickering or flashing occurs at 20 Hertz.
Refer to the section on script techniques
__________________________________________________________
3.8 Allow the user to turn on and off rendering of images.
[Priority 3]
Techniques:
Refer to techniques for checkpoint 3.1.
__________________________________________________________
3.9 Allow the user to turn on and off author-specified forwards that
occur after a time delay and without user intervention.
[Priority 3]
Techniques:
Content refresh according to an author-specified time interval
can be achieved with the following markup in HTML:
The user agent should allow the user to disable this type of
content refresh.
Although no HTML specification defines this behavior formally,
some user agents support the use of the META element to refresh
the current page after a specified number of seconds, with the
option of replacing it by a different URI. Instead of this
markup, authors should use server-side redirects (with HTTP).
User agents can provide a link to other content rather than
changing the content automatically.
User agents may also prompt the user and ask whether to
continue with forwards.
__________________________________________________________
For example, when forwarding has been turned off, offer a
static link to the target.
3.10 Allow the user to turn on and off automatic content refresh.
[Priority 3]
For example, when turned off, indicate to the user that content
needs refreshing and allow the user to do so through the user
interface.
Guideline 4. Ensure user control over styles
In addition to the techniques below, refer also to the section on user
control of style.
Checkpoints for fonts and colors:
4.1 Allow the user to control font family. [Priority 1]
Techniques:
+ Implement the CSS 'font-family' property.
+ Allow the user to override the author's specified fonts.
+ Inherit font information from user's settings for the
operating system.
__________________________________________________________
4.2 Allow the user to control the size of text. [Priority 1]
For example, allow the user to specify a font family and style
directly through the user interface. Or, allow the user to give
preferences through a user style sheet. Or allow the user to
magnify text.
Techniques:
+ Implement the CSS 'font-size' property.
+ Allow the user to configure the user agent to ignore
author-specified font size.
+ Inherit font size information from user's settings for the
operating system.
__________________________________________________________
4.3 Allow the user to control foreground color. [Priority 1]
Techniques:
+ Implement the CSS 'color' and 'border-color' properties.
+ Allow the user to specify minimal contrast between foreground
and background colors, adjusting colors dynamically to meet
those requirements.
+ Allow the user to impose a specific foreground color,
ignoring author-supplied colors.
+ Inherit foreground color information from user's settings for
the operating system.
__________________________________________________________
4.4 Allow the user to control background color. [Priority 1]
Techniques:
+ Implement the CSS 'background-color' property and other
background properties.
+ Allow the user to impose a specific background color,
ignoring author-supplied colors.
+ Inherit background color information from user's settings for
the operating system.
__________________________________________________________
4.5 Allow the user to control selection highlighting (e.g., foreground
and background color). [Priority 1]
Techniques:
+ For instance, in X Windows, the following resources controls
the selection colors in Netscape Navigator:
"*selectForeground" and "*selectBackground".
+ Implement the CSS 2 "HighLightText and "Highlight" predefined
color values ([CSS2], section 18.2).
+ Inherit selection/focus information from user's settings for
the operating system.
__________________________________________________________
4.6 Allow the user to control focus highlighting (e.g., foreground and
background color). [Priority 1]
Checkpoints for applets and animations:
4.7 Allow the user to control animation rate. [Priority 2]
Checkpoints for video.
4.8 Allow the user to control video frame rates. [Priority 1]
4.9 Allow the user to control the position of captions. [Priority 1]
4.10 Allow the user to start, stop, pause, fast forward, and rewind
video. [Priority 2]
Checkpoints for audio:
4.11 Allow the user to control audio playback rate. [Priority 1]
Note. User agents may not be able to control the playback rate
for some audio formats.
4.12 When the user agent renders audio natively, allow the user to
control the audio volume. [Priority 2]
4.13 Allow the user to start, stop, pause, fast forward, and rewind
audio. [Priority 2]
Checkpoints for synthesized speech:
4.14 Allow the user to control synthesized speech playback rate.
[Priority 1]
Techniques:
+ In CSS2, use the 'speech-rate' property.
__________________________________________________________
4.15 Allow the user to control synthesized speech volume. [Priority 1]
4.16 Allow the user to control synthesized speech pitch, gender, and
other articulation characteristics. [Priority 2]
Checkpoints for user interface accessibility:
4.17 Allow the user to select from available author and user style
sheets, including no author or user style sheets. [Priority 1]
Note. The browsers default style sheet is always present.
Techniques:
+ Make available "class" and "id" information so that users can
override styles.
+ Allow the user to define custom styles for "class" and "id"
attributes specified in the document.
__________________________________________________________
4.18 Allow the user to control user agent-initiated spawned viewports.
[Priority 2]
For example, in HTML, allow the user to control the process of
opening a document in a new target frame or a viewport created
by author-supplied scripts. In SMIL 1.0, allow the user to
control viewports created with show="new". Control may involve
prompting the user to confirm or cancel the viewport creation.
Users may also want to control the size or position of the
viewport and to be able to close the viewport (e.g., with the
"back" functionality).
Techniques:
User agents may:
+ Allow users to turn off support for spawned viewports
entirely
+ Prompt them before spawning a viewport
For example, user agents may recognize the HTML construct
target="_blank" and spawn the window according to the user's
preference.
__________________________________________________________
Guideline 5. Observe system conventions and standard interfaces
Checkpoints for content accessibility:
5.1 Provide accessible APIs to other technologies. [Priority 1]
5.2 Conform to W3C Document Object Model specifications and export
interfaces defined by those specifications. [Priority 1]
For example, refer to the DOM ([DOM1], [DOM2]). User agents
should export these interfaces using available operating system
conventions.
Techniques:
A Document Object Model (DOM) is an interface to a standardized
tree structure representation of a document. This interface
allows authors to access and modify the document with
client-side scripting language (e.g., JavaScript) in a
consistent manner across scripting languages. As a standard
interface, a DOM makes it easier not just for authors but for
assistive technology developers to extract information and
render it in ways most suited to the needs of particular users.
Information of particular importance to accessibility that must
be available through the DOM includes:
+ Content, including alternative equivalents.
+ Style sheet information (for user control of styles).
+ Script and event handlers (for device-independent control of
behavior).
+ The document structure (for navigation, creation of
alternative views).
User agents should implement W3C DOM Recommendations, including
DOM Level 1 [DOM1] and DOM Level 2 [DOM2]]. The W3C
Recommendation for DOM Level 1 ([DOM1]) provides access to HTML
and XML document information. The DOM Level 2 ([DOM2]) is made
of a set of core interfaces to create and manipulate the
structure and contents of a document and a set of optional
modules. These modules contain specialized interfaces dedicated
to XML, HTML, an abstract view, generic stylesheets, Cascading
Style Sheets, Events, traversing the document structure, and a
Range object.
It is important to note that DOM is designed to be used on a
server as well as a client and therefore a lot of user
interface-specific information such as screen coordinate
information is not relevant and not addressed by the DOM
specification.
Assistive technologies also require information about browser
highlight mechanisms (e.g., the selection and focus) that may
not be available through the W3C DOM.
The DOM Level 1 specification states that "DOM applications may
provide additional interfaces and objects not found in this
specification and still be considered DOM compliant."
Note. The WAI Protocols and Formats Working Group is focusing
its efforts on the DOM as the conduit from which to extract
accessibility information and enhance the accessibility of a
rendered document through a user agent.
__________________________________________________________
Checkpoints for user interface accessibility:
5.3 Use accessibility resources and conventions of the operating
system and supported programming languages, including those for
plug-ins and virtual machine environments. [Priority 1]
For instance, if the user agent supports Java applets and
provides a Java Virtual Machine to run them, the user agent
should support the proper loading and operation of a Java
native assistive technology. This assistive technology can
provide access to the applet as defined by Java accessibility
standards.
Techniques:
The operating system application programming interfaces (APIs)
that support accessibility are designed to provide a bridge
between the standard user interface supported by the operating
system and alternative user interfaces developed by third-party
assistive technology vendors to provide access to persons with
disabilities. Applications supporting these APIs are therefore
generally more compatible with third-party assistive
technology.
The User Agent Accessibility Guidelines Working Group strongly
recommends using and supporting APIs that improve accessibility
and compatibility with third-party assistive technology.
Third-party assistive technology can use the accessibility
information provided by the APIs to provide an alternative user
interface for various disabilities.
The following is an informative list of currently public APIs
that promote accessibility:
+ Microsoft Active Accessibility ([MSAA]) in Windows 95/98/NT
versions.
+ Sun Microsystems Java Accessibility API ([JAVAAPI]) in Java
Code.
Many operating systems have built-in accessibility features for
improving the usability of the standard operating system by
persons with disabilities. When designing software that runs
above an underlying operating system, developers should ensure
that the application:
1. Makes use of operating system level features. See the
appendix of accessibility features for some common operating
systems.
2. Inherits operating system settings related to accessibility.
Pertinent settings include font and color information as well
as other pieces of information discussed in this document.
Write output to and take input from standard system APIs rather
than directly from hardware controls where possible. This will
enable the I/O to be redirected from or to assistive technology
devices - for example, screen readers and Braille devices often
redirect output (or copy it) to a serial port, while many
devices provide character input, or mimic mouse functionality.
The use of generic APIs makes this feasible in a way that
allows for interoperability of the assistive technology with a
range of applications.
User agents should use standard rather than custom controls
when designing user agents. Third-party assistive technology
developers are more likely able to access standard controls
than custom controls. If you must use custom controls, review
them for accessibility and compatibility with third-party
assistive technology.
For information about rapid access to Microsoft Internet
Explorer's DOM through COM, refer to [BHO].
__________________________________________________________
5.4 Provide programmatic read and write access to user agent
functionalities and user interface controls. [Priority 1]
For example, ensure that assistive technologies have access to
information about the current input configuration so that they
can trigger functionalities through keyboard events, mouse
events, etc. Refer also to checkpoint 5.3.
5.5 Implement selection and focus mechanisms and make the selection
and focus available to users and through APIs. [Priority 1]
Refer also to checkpoint 7.1 and checkpoint 5.4. Note. This
checkpoint is an important special case of checkpoint 5.4.
5.6 Provide programmatic notification of changes to content and user
interface controls (including selection and focus).
[Priority 1]
Refer also to checkpoint 5.3.
5.7 Provide programmatic exchange of information in a timely manner.
[Priority 2]
This is important for synchronous alternative renderings and
simulation of events.
5.8 Follow operating system conventions and accessibility settings. In
particular, follow conventions for user interface design,
default keyboard configuration, product installation, and
documentation. [Priority 2]
Refer also to checkpoint 10.5.
Techniques:
Develop the UA User Interface (UI) with standard interface
components per the target platform(s). Most major operating
system platforms provide a series of design and usability
guidelines; these should be followed when possible (see
platforms below). These checklists, style guides, and human
interface guidelines provide very valuable information for
developing applications (e.g., UAs) for any platform/operating
system/GUI.
For instance, software should use the standard interface for
keyboard events rather than working around it.
Evaluate your standard interface components on the target
platform against any built in operating system accessibility
functions (see Appendix 8) and be sure your UA operates
properly with all these functions.
For example, take caution with the following:
+ Microsoft Windows supports an accessibility function called
"High Contrast". Standard window classes and controls
automatically support this setting. However, applications
created with custom classes or controls must understand how
to work with the "GetSysColor" API to ensure compatibility
with High Contrast.
+ Apple Macintosh supports an accessibility function called
"Sticky Keys". Sticky Keys operates with keys the operating
system recognizes as modifier keys, and therefore a custom UA
control should not attempt to define a new modifier key.
Some guidelines for specific platforms:
+ "Macintosh Human Interface Guidelines" [APPLE-HI] Apple
Computer Inc.
+ "IBM Guidelines for Writing Accessible Applications Using
100% Pure Java" [JAVA-ACCESS].
+ "An ICE Rendezvous Mechanism for X Window System Clients"
[ICE-RAP].
+ "Information for Developers About Microsoft Active
Accessibility" [MSAA].
+ "The Inter-Client communication conventions manual" [ICCCM].
+ "Lotus Notes accessibility guidelines" [NOTES-ACCESS].
+ "Java accessibility guidelines and checklist"
[JAVA-CHECKLIST].
+ "The Java Tutorial. Trail: Creating a GUI with JFC/Swing"
[JAVA-TUT].
+ "The Microsoft Windows Guidelines for Accessible Software
Design" [MS-SOFTWARE].
General guidelines for producing accessible software:
+ "Accessibility for applications designers" [MS-ENABLE].
+ "Application Software Design Guidelines" [TRACE-REF].
+ "Designing for Accessibility" [SUN-DESIGN].
+ "EITAAC Desktop Software standards" [EITAAC].
+ "Requirements for Accessible Software Design" [ED-DEPT].
+ "Software Accessibility" [IBM-ACCESS].
+ Towards Accessible Human-Computer Interaction" [SUN-HCI].
+ "What is Accessible Software" [WHAT-IS].
+ Accessibility guidelines for Unix and X Window applications
[XGUIDELINES].
Follow System Conventions for loading Assistive Technologies:
User agents should follow operating system or application
environment (e.g., Java) conventions for loading assistive
technologies. In the case of Java applets, the browser's Java
Virtual Machine should follow the Sun convention for loading an
assistive technology. Writing an application that follows the
Java system conventions for accessible software does not allow
the applet to be accessible if an assistive technology designed
for that environment cannot be run to make the applet
accessible. Refer to the appendix on loading assistive
technologies for DOM access for information about how an
assistive technology developer can load its software into a
Java Virtual Machine.
__________________________________________________________
Guideline 6. Implement accessible specifications
Checkpoints for content accessibility:
6.1 Implement the accessibility features of supported specifications
(markup languages, style sheet languages, metadata languages,
graphics formats, etc.). [Priority 1]
Note. The Techniques Document [UA-TECHNIQUES] discusses
accessibility features of W3C specifications.
Techniques:
+ The accessibility features of Cascading Style Sheets ([CSS1],
[CSS2]) are described in "Accessibility Features of CSS"
[CSS-ACCESS]. Note that CSS 2 includes properties for
controlling synthesized speech styles.
+ The accessibility features of SMIL 1.0 [SMIL] are described
in "Accessibility Features of SMIL" [SMIL-ACCESS].
+ The following is a list of accessibility features of HTML 4.0
[HTML40] in addition to those described in techniques for
checkpoint 2.1:
o The CAPTION element (section 11.2.2) for rich table
captions.
o Table elements (THEAD, TBODY, TFOOT (section 11.2.3),
COLGROUP, and COL (section 11.2.4) that group table
rows and columns into meaningful sections.
o Attributes ( "scope", "headers", and "axis", section
11.2.6) that non-visual browsers may use to render a
table in a linear fashion, based on the semantically
significant labels.
o The "tabindex" attribute (section 17.11.1) for assigning
the order of keyboard navigation within a document.
o The "accesskey" attribute (section 17.11.2) for
assigning keyboard commands to active components such as
links and form controls.
__________________________________________________________
6.2 Conform to W3C specifications when they are appropriate for a
task. [Priority 2]
For instance, for markup, implement HTML 4.0 [HTML40] or XML
1.0 [XML]. For style sheets, implement CSS ([CSS1], [CSS2]).
For mathematics, implement MathML [MATHML]. For synchronized
multimedia, implement SMIL 1.0 [SMIL]. For access to the
structure of HTML or XML documents, implement the DOM ([DOM1],
[DOM2]). Refer also to checkpoint 5.2.
Note. For reasons of backward compatibility, user agents should
continue to support deprecated features of specifications. The
current guidelines refer to some deprecated language features
that do not necessarily promote accessibility but are widely
deployed.
Guideline 7. Provide navigation mechanisms
Checkpoints for user interface accessibility:
7.1 Allow the user to navigate viewports (including frames).
[Priority 1]
Note. For example, when all frames of a frameset are displayed
side-by-side, allow the user to navigate among them with the
keyboard. Or, when frames are accessed or viewed one at a time
(e.g., by a text browser or speech synthesizer), provide a list
of links to other frames. Navigating into a viewport makes it
the current viewport.
Techniques:
+ Some operating systems provide a means to navigate among all
open windows using multiple input devices (e.g., keyboard and
mouse). This technique would suffice for switching among user
agent viewports that are separate windows. However, user
agents may also provide a mechanism to shift the focus among
user agent windows, independent of the standard operating
system mechanism.
+ Consult the section on frame techniques.
__________________________________________________________
7.2 For user agents that offer a browsing history mechanism, when the
user returns to a previous view, restore the point of regard in
the viewport. [Priority 1]
For example, when users navigate "back" and "forth" among
views, for each view they should find the viewport position
where they left it.
7.3 Allow the user to navigate just among cells of a table (notably
left and right within a row and up and down within a column).
[Priority 1]
Note. Navigation techniques include keyboard navigation from
cell to cell (e.g., using the arrow keys) and page up/down
scrolling. Refer also to checkpoint 1.1 and checkpoint 5.4.
Techniques:
Refer to the section on table navigation.
__________________________________________________________
7.4 Allow the user to navigate all active elements. [Priority 1]
Navigation mechanisms may range from sequential (e.g.,
sequential navigation) to direct (e.g., by entering link text)
to searching on active elements only (e.g., based on form
control text, associated labels, or form control names). Note.
This checkpoint is an important special case of checkpoint 7.7.
7.5 Allow the user to navigate just among all active elements.
[Priority 2]
Note. In checkpoint 7.4, navigation may include non-active
elements in addition to active elements.
Techniques:
2.7.1 Sequential navigation techniques
Allow the user to sequential navigate all active elements using
a single keystroke. User agents might also provide other
sequential navigation mechanisms for particular element types
or semantic unit. For example "Find the next table" or "Find
the previous form".
It is important that application developers maintain a logical
element navigation order. For instance, users may use the
keyboard to navigate among elements or element groups and using
the arrow keys within a group of elements. One example of a
group of elements is a set of radio buttons. Users should be
able to navigate to the group of buttons, then be able to
select each button in the group. Similarly, allow users to
navigate from table to table, but also among the cells within a
given table (up, down, left, right, etc.)
+ How to indicate that something is in navigation order in
Java: A component is inclusive in the sequential navigation
order when added to a panel and its isFocusTraversable()
method returns true. A component can be removed from the
navigation order by simply extending the component,
overloading this method, and returning false.
+ Give the users the option of navigating to and activating a
link, or just moving the focus to the link. When the user
returns to the page after following the link, restore focus
to that link.
+ Many user agents today allow users to navigate sequentially
by tabbing -- for example, using the "tab" key for forward
navigation and "shift-tab" for reverse navigation. Because
the "tab" key is typically on one side of the keyboard while
arrow keys are located on the other, users should be allowed
to configure the user agent so that sequential navigation is
possible with keys that are physically closer to the arrow
keys. Refer also to checkpoint 10.3.
2.7.2 Direct navigation techniques
Excessive use of sequential navigation can reduce the usability
of software for both disabled and non-disabled users. Direct
access (e.g., through keyboard shortcuts) should also be
possible. Providing direct access involves:
+ Assigning each active element a unique identifier (or use the
identifier provided by the author, e.g., "accesskey" in
HTML). For example number each active element in a document.
+ Documenting how the user may access elements.
+ Allowing direct access by element content (e.g., the first
letter of element content).
+ Allowing direct access to a table cell by its row/column
position.
__________________________________________________________
7.6 Allow the user to search for rendered text content, including text
equivalents of visual and auditory content. [Priority 2]
Note. Use operating system conventions for marking the result
of a search (e.g., selection and focus).
Techniques:
+ Allow users to search for element content and attribute
values (human-readable ones).
+ Allow forward and backward searching from the point of
regard, beginning of document, or end of document.
+ Allow users to search the document source view.
+ For forms, allow users to find required controls. Allow users
to search on labels as well as content of some controls.
+ Allow the user to search among just text equivalents of other
content.
+ For multimedia presentations:
o Allow users to search and examine time-dependent media
elements and links in a time-independent manner. For
example, present a static list of time-dependent links.
o Allow users to find all media elements active at a
particular time in the presentation.
o Allow users to view a list of all media elements or
links of the presentations sorted by start or end time
or alphabetically.
o For frames, allow users to search for content in all
frames (without having to be in a particular frame).
__________________________________________________________
7.7 Allow the user to navigate according to structure. [Priority 2]
For example, allow the user to navigate familiar elements of a
document: paragraphs, tables, headers, lists, etc. Note. Use
operating system conventions to indicate navigation progress
(e.g., selection and focus).
Techniques:
+ DOM is minimal (tree navigation)
+ Best navigation will involve a mix of source tree information
and rendered information.
+ May use commonly understood document models rather than
strict Document Type Definition (DTD) navigation. E.g.,
properly nesting headers in HTML. Headers should be used only
to convey hierarchy, not for graphical side-effects.
+ Goal of simplifying the structure view as much as possible.
+ Allow the user to control level of detail/ view of structure.
+ Depth first as well as breadth first possible. Allow
next/previous sibling, up to parent, and end of element.
+ Navigation of synchronized multimedia: allow users to stop,
pause, fast forward, advance to the next clip, etc.
+ Allow the user to navigate characters, words, sentences,
paragraphs, screenfuls, and other language-dependent pieces
of text content. This may be particularly useful with a
speech-based user interface. Precise and flexible navigation
of this kind with a system cursor is often useful when
browsing with accessibility aids. Evidence of this point is
that the leading Windows screen readers have super-imposed
such navigation on a popular web browser that does not
natively support it (e.g., Winvision, Window-Eyes, and JAWS
with Internet Explorer).
Skipping navigation bars:
Author-supplied navigation mechanisms such as navigation bars
at the top of each page may force users with screen readers or
some physical disabilities to wade through numerous links on
each page of a site. User agents may facilitate browsing for
these users by allowing them to skip recognized navigation bars
(e.g., through a configuration option). Some techniques for
doing so include:
1. Provide a functionality to jump to the first non-link
content.
2. In HTML, the MAP element may be used to mark up a navigation
bar (even when there is no associated image). Thus, users
might ask that MAP elements not be rendered in order to hide
links inside the MAP element. Note. Starting in HTML 4.0, the
MAP element allows block content, not just AREA elements.
__________________________________________________________
7.8 Allow the user to configure structured navigation. [Priority 3]
For example, allow the user to navigate only paragraphs, or
only headers and paragraphs, etc.
Techniques:
+ Allow the user to navigate by element type.
+ Allow the user to navigate HTML elements that share the same
"class" attribute.
+ Allow the user to expand or shrink portions of the structured
view (control detail level) for faster access to important
parts content.
__________________________________________________________
Guideline 8. Orient the user
Checkpoints for content accessibility:
8.1 Convey the author-specified purpose of each table and the
relationships among the table cells and headers. [Priority 1]
For example, provide information about table headers, how
headers relate to cells, table caption and summary information,
cell position information, table dimensions, etc. Note. This
checkpoint is an important special case of checkpoint 2.1.
Techniques:
+ Refer to the section on table techniques
+ Allow the user to access this information on demand (e.g., by
activating a menu or keystroke).
__________________________________________________________
8.2 Indicate whether a focused link has been marked up to indicate
that following it will involve a fee. [Priority 2]
Note. This checkpoint is an important special case of
checkpoint 8.3. "Common Markup for micropayment per-fee-links"
[MICROPAYMENT] describes how authors may mark up micropayment
information in an interoperable manner. This information may be
provided through the standard user interface provided the
interface is accessible. Thus, any prompt asking the user to
confirm payment must be accessible.
Techniques:
+ Refer to the section on link techniques.
+ Allow the user to access this information on demand (e.g., by
activating a menu or keystroke for a focused link).
__________________________________________________________
8.3 Provide information to help the user decide whether to follow a
focused link. [Priority 2]
Note. Useful information includes: whether the link has already
been visited, whether it designates an internal anchor, the
type of the target resource, the length and size of an audio or
video clip that will be started, and the expected natural
language of target resource.
Techniques:
+ Refer to the section on link techniques.
+ Allow the user to access this information on demand (e.g., by
activating a menu or keystroke).
+ Implement CSS ':visited' and ':link' pseudo-classes, with
':before' class and the 'content' property to insert text
before a link such as "visited" or "un-visited".
__________________________________________________________
Checkpoints for user interface accessibility:
8.4 Provide a mechanism for highlighting and identifying (through a
standard interface where available) the current viewport,
selection, and focus. [Priority 1]
Note. This includes highlighting and identifying frames. Refer
also to checkpoint 9.1.
Techniques:
+ If colors are used to highlight the current viewport,
selection, or focus, allow the user to set preferred colors
and to ensure sufficient contrasts.
+ If the current viewport is a window, allow the user to cause
the window to pop to the foreground.
+ If the current viewport is a frame or the user doesn't want
windows to pop to the foreground, use colors, reverse videos,
or other visual clues to indicate the current viewport. For
speech or Braille output, render the title or name of a frame
or window and indicate changes in the current viewport.
+ Use operating system conventions, where available, for
specifying selection and focus (e.g., schemes in Windows).
+ Implement the CSS pseudo-classes ':hover', ':active', and
':focus'. This will allow users to modify focus presentation
in user style sheets.
Refer also to the section on frame techniques
The following image illustrates the use by Opera 3.6 of a solid
line border to indicate focus:
Example of a solid line border used to indicate the focus in
Opera 3.60
The following image illustrates the use of system highlight
colors to indicate focus:
Example of system highlight colors used to indicate the focus
by the accessible browser project
The following image illustrates the use of a dotted line border
to indicate focus:
Example of dotted line border used to indicate the focus in
Internet Explorer 5.0 and Netscape Navigator 4.7
__________________________________________________________
8.5 Provide an outline view of a resource built from the resource's
structural elements (e.g., frames, headers, lists, forms,
tables, etc.) [Priority 2]
For example, for each frame in a frameset, provide a table of
contents composed of headers where each entry in the table of
contents links to the header in the document.
Techniques:
+ Use commonly understood document models rather than strict
DTD navigation. E.g., properly nesting headers in HTML.
+ For documents that don't use structure properly, user agents
may try to create an outline from presentation elements used
(insufficiently) to convey structure.
+ Allow the user to shrink and expand the outline view
selectively.
+ Provide context-sensitive navigation: for instance, when the
user navigates to a list or table, provide locally useful
navigation mechanisms (e.g., within a table, cell-by-cell
navigation) using similar input commands.
+ Refer to the section on list techniques.
The following technique ideas were provided by the National
Information Standards Organization [NISO]:
A "Navigation Control Center" (NCC) (NCC) resembles a traditional
table of contents, but it is more. The NCC contains links to all
headings at all levels in the book. In addition to the headings,
links to all pages are inserted. Finally we include in the NCC
links to all items that the reader may select to turn off for
reading. For example, if the reader has the automatic reading of
footnotes turned off, there must be a way to quickly get back to
that information. For this reason, the reference to the footnote is
placed in the NCC and the reader can go to the reference,
understand the context for the footnote, and then read the
footnote. All items that have the option of turning off automatic
reading can be reached through the NCC.
Once the reader is at a desired location and wishes to begin
reading, the navigation process changes. Of course, the reader may
elect to read sequentially, but often some navigation is required
(e.g., frequently people navigate forward or backward one word or
character at a time). Moving from one sentence or paragraph at a
time is also needed. This type of local navigation is different
from the global navigation used to get to the location of what you
want to read. It is frequently desirable to move from one block
element to the next. For example, moving from a paragraph to the
next block element which may be a list, blockquote, or sidebar is
the normally expected mechanism for local navigation.
__________________________________________________________
8.6 Allow the user to configure the outline view. [Priority 3]
For example, allow the user to control the level of detail of
the outline. Refer also to checkpoint 8.5. Refer also to
checkpoint 5.4.
8.7 Allow the user to configure what information about links to
present. [Priority 3]
Note. Using color as the only distinguishing factor between
visited and unvisited links does not suffice since color may
not be perceivable by all users or rendered by all devices.
Refer also to checkpoint 8.3.
Techniques:
+ Allow the user to access this information on demand (e.g., by
activating a menu or keystroke).
+ Implement CSS ':visited' and ':link' pseudo-classes, with
':before' class and the 'content' property to insert text
before a link such as "visited" or "un-visited".
__________________________________________________________
8.8 Provide a mechanism for highlighting and identifying (through a
standard interface where available) active elements.
[Priority 3]
Note. User agents may satisfy this checkpoint by implementing
the appropriate style sheet mechanisms, such as link
highlighting.
8.9 Maintain consistent user agent behavior and default configurations
between software releases. Consistency is less important than
accessibility and adoption of operating system conventions.
[Priority 3]
In particular, make changes conservatively to the layout of
user interface controls, behavior of existing functionalities,
and default keyboard configuration.
Guideline 9. Notify the user of content and viewport changes
Checkpoints for user interface accessibility:
9.1 Provide information about user agent-initiated content and
viewport changes through the user interface and through APIs.
[Priority 1]
For example, inform the users when a script causes a popup menu
to appear.
Techniques:
+ Refer to the section on frame techniques
+ Render the changed content graphically.
+ Highlight the current viewport.
+ Emit an audible signal when a change occurs.
+ Make DOM methods fire a "change" event that can be trapped.
__________________________________________________________
9.2 Ensure that when the selection or focus changes, it is in a
viewport after the change. [Priority 2]
Techniques:
+ There are time when the focus changes (e.g., link navigation)
and the viewport must be moved to track it. There are other
times when the viewport changes position (e.g., scrolling)
and the focus must be moved to follow it. In both cases, the
focus (or selection) is in the viewport after the change.
+ Make sure that search windows do not place the new focus that
is the found object under a search popup.
+ When the focus changes, "register" the newly focused element
in the navigation sequence; sequential navigation should
start from there.
+ Only change selection/focus in the current viewport, not
other viewports.
__________________________________________________________
9.3 Prompt the user to confirm any form submission triggered
indirectly, that is by any means other than the user activating
an explicit form submit control. [Priority 2]
Techniques:
+ Put up a dialog indicating the form will be submitted if it
is done by an onChange, after a certain time, or for other
script-based submission. Allow the user to suppress these
dialogs for good.
+ If the submit button is not the last control in the form, and
no controls after it have been focused, put up a dialog
pointing this out/asking if the user has filled in the
information after the button.
+ If a Javascript submission is fired, allow the user to ask
for it to be intercepted and trigger the dialog mentioned
above.
__________________________________________________________
For example, do not submit a form automatically when a menu
option is selected, when all fields of a form have been filled
out, on a mouseover event, etc.
9.4 Allow the user to configure notification preferences for common
types of content and viewport changes. [Priority 3]
For example, allow the user to choose to be notified (or not)
that a script has been executed, that a new viewport has been
opened, that a pulldown menu has been opened, that a new frame
has received focus, etc.
Techniques:
+ Refer to the section on frame techniques
+ Allow the user to specify an element type for which
notification should be disabled (e.g., table, body, img, ...)
+ Allow the user to disable notification of changes to CSS
properties
+ Allow the user to disable notification of images that are
changed
__________________________________________________________
9.5 When loading content (e.g., document, video clip, audio clip,
etc.) indicate what portion of the content has loaded and
whether loading has stalled. [Priority 3]
Techniques:
Status information - on resource loading - should be provided
in a device-independent manner. Techniques include text and
non-text status indicators. Users should be able to request
status information or have it rendered automatically. User
agents may allow users to configure when status information
should be rendered (e.g., by hiding or showing the status bar).
Screen readers may provide access on demand (e.g., through the
keyboard) to the most recent status information, or to announce
the new information whenever it changes.
Useful status information:
+ Document proportions (numbers of lines, pages, width, etc.)
+ Number of elements of a particular type (e.g., tables)
+ The viewport is at the beginning or end of the document.
+ Size of document in bytes.
User agents may allow users to configure what status
information they want rendered. Allow users to access status
information on demand through a keyboard or other shortcut.
Indicate when loading has finished, for example with a
percentage indication or a special message. Indication must not
depend on a particular output device.
__________________________________________________________
9.6 Indicate the relative position of the viewport in content (e.g.,
the percentage of an audio or video clip that has been played,
the percentage of a Web page that has been viewed, etc.).
[Priority 3]
Note. The user agent may calculate the percentage according to
focus position, selection position, or viewport position,
depending on how the user has been browsing.
Techniques:
+ Provide a scrollbar for the viewport.
+ Give the size of the document as well, so that users may
decide whether to download for offline viewing. For example,
the playing time of an audio file could be stated in terms of
hours, minutes, and seconds. The size of a primarily text
based web page might be stated in both kilobytes and screens,
where a screen of information is calculated based on the
current dimensions of the viewport.
+ List the current "page" as page X of a total of Y pages.
+ Use a variable pitch audible signal to indicate position.
+ Keep the information numerically and generate the output on
user request. See new HTML work on Forms for further examples
(a slider is like a dial is like a menu of lots of
options...)
+ Provide standard markers for specific percentages through the
document (mile posts)
+ Provide markers for positions relative to some position - a
user selected point, the bottom, the H1, etc.
+ Put a marker on the scrollbar, or a highlight at the bottom
of the page while scrolling (so you can see what was the
bottom before you started scrolling
__________________________________________________________
Guideline 10. Allow configuration and customization
Checkpoints for user interface accessibility:
10.1 Provide information directly to the user and through APIs about
the current user-specified input configuration (e.g., keyboard
or voice bindings specified through the user agent's user
interface). [Priority 1]
Techniques:
If the currently active configuration changes locally (e.g., a
search prompt opens, changing the keyboard mapping for the
duration of the prompt), alert the user. The user must also be
informed of the changed (currently active) configuration. Do
not rely on visual or audio cues alone to alert the user of the
change. Do not limit the user to only one type of alert
mechanism. Do not rely on visual cues (e.g., the underlining of
an accelerator key) alone to inform the user of changes in the
configuration.
Named configurations are easier to remember. This is especially
important for persons with certain types of cognitive
disabilities. For example, if the invocation of a search prompt
changes the currently active configuration, the user may
remember more easily which keystrokes are active in search mode
if alerted that there is a "Search Mode". Context-sensitive
help (if available) should reflect the change in mode, and a
list of keybindings for the current mode should be readily
available to the user.
2.10.1 Documentation of sequential navigation order
+ Specified by the HTML 4.0 "tabindex" attribute ([HTML40],
section 17.11.1).
+ Provide a list of form controls according to the sequential
navigation order of the form. This allows users to know
whether, for example, a submit button is the last control in
a form or whether the user must activate controls that follow
it.
+ Provide a structured view of form controls (e.g., those
grouped by LEGEND or OPTGROUP in HTML) along with their
labels.
2.10.2 Documentation of keyboard shortcuts
+ Specified by the HTML 4.0 "accesskey" attribute ([HTML40],
section 17.11.2).
+ Use system conventions to indicate the current configuration.
+ Document the default configuration.
+ Allow direct access to active elements (links, form controls,
etc.). For instance, through a menu that allows users to
enter a link number of link text and to move the focus there.
+ Allow the user to separate setting the focus and activating
the control. For links, first-time users of a page may want
to hear link text (focus) before deciding whether to follow
the link (activate). More experienced users of a page would
prefer to follow the link directly, without the intervening
focus step.
2.10.3 Configuration of the user interface
+ Allow the user to configure the user agent so that the
current viewport is automatically maximized. For example, the
parent window of the browser would automatically be maximized
when launched, and each child window would automatically be
maximized when it received input focus. Maximizing does not
necessarily mean occupying the whole screen or parent window;
it means expanding the current window so that the need to
scroll horizontally or vertically is as little as possible.
__________________________________________________________
10.2 Provide information directly to the user and through APIs about
the current author-specified input configuration (e.g.,
keyboard bindings specified in content such as by "accesskey"
in HTML 4.0). [Priority 2]
Techniques:
Distinguish the following classes of user input configurations:
+ What are the defaults "out of the box"?
+ What are the current settings different from those out of the
box.
+ What are those in effect for the current document only?
+ What are those that have been overridden by the configuration
of the current document? Also, how to access functionalities
no longer available due to the current input configuration.
In association with local (e.g., this page only) and
off-default bindings, provide information about how to work
around the override.
Note that user support personnel, particularly remote support
personnel, will need the "departures from shipping defaults"
view for orientation.
The above classes may be distinguished by displayed properties
in a combined presentation as well as by filtering to present
only a restricted class.
Some reserved keyboard shortcuts are listed in the appendix on
accessibility features of some operating systems.
In case of conflicts between author-supplied configuration and
user-supplied, operating system defaults, or user agent default
configurations, here is some possible behavior:
+ Do not override default system and user agent controls, but
alert the user of author-supplied configuration and provide a
pass-through mechanism to allow author-specified
configurations that conflict with default UA or OS
keybindings to be invoked.
+ Allow author-defined configurations to override user agent
and operating system configurations, but alert the user of
the conflicts and provide a pass-through mechanism so that
the conflicting user agent or operating system configurations
can be invoked.
+ Remap author-supplied configurations to currently unused
keystrokes, voice commands, etc. and alert the user to which
configurations have been remapped.
__________________________________________________________
10.3 Allow the user to change and control the input configuration.
Users should be able to activate a functionality with a
single-stroke (e.g., single-key, single voice command, etc.).
[Priority 2]
For voice-activated browsers, allow the user to modify what
voice commands activate functionalities Similarly, allow the
user to modify the graphical user interface for quick access to
commonly used functionalities (e.g., through buttons).
Techniques:
Provide a convenient interface for allowing users to control
input configurations. For example, allow them to select from
available options, rather than having them enter combinations
themselves. This will speed up configuration and reduce
questions to support staff later on how to configure the user
agent.
User agents that allow users to customize or reconfigure
mappings from keyboard, voice, etc. to user agent
functionalities should allow each mapping to be accompanied by
a description so that the user can understand the mapping. For
example, if "Control-P" maps to a print functionality, a short
description would be "Print" or "Print setup".
+ Profiles
+ Default values
+ Device-independent configuration
When using a physical keyboard, some users require single-key
access, others require that keys activated in combination be
physically close together, while others require that they be
spaced physically far apart. When allowing users to configure
keyboard access to functionalities, user agents must consider
operating system conventions, author-specified shortcuts, and
user preferences. The user agent's default configuration should
include shortcuts for frequently performed actions and should
respect operating system conventions.
To illustrate problems some users with poor motor control
encounter and why single-key access is important: Put the
keyboard Repeat Delay to very short and the Repeat rate to very
fast (or whatever rate is bothersome). The slightest touch or
accidental bump will generate a key press, illustrating the
challenge key combinations pose.
User agents, to allow the user to turn on and off
author-specified keyboard configurations, may offer a checkbox
in the keyboard mapping dialog to that would toggle the support
for author-specified keyboard configurations. In HTML 4.0,
authors may specify keyboard behavior with the "tabindex" and
"accesskey" attributes ([HTML40], sections 17.11.1 and
17.11.2, respectively).
Allow users to restore easily the user agent's default
configuration.
__________________________________________________________
10.4 Use operating system conventions to indicate the input
configuration. [Priority 2]
For example, on some operating systems, if a functionality is
available from a menu, the letter of the key that will activate
that functionality is underlined. Note. This checkpoint is an
important special case of checkpoint 5.8.
Techniques:
In some operating systems, information about shortcuts is
rendered visually using an underscore under a character in a
menu item or button corresponding to the shortcut key activated
with an ALT+character. For menu accelerators the text in the
menu item is often followed by a CNTRL+function key. These are
conventions used by the Sun Java Foundations Classes [JAVA-TUT]
and Microsoft Foundations Classes for Windows.
__________________________________________________________
10.5 Avoid default input configurations that interfere with operating
system conventions. [Priority 2]
For example, the default configuration should not include
"Alt-F4" or "Control-Alt-Delete" on operating systems where
that combination has special meaning to the operating system.
In particular, default configurations should not interfere with
the mobility access keyboard modifiers reserved for the
operating system. Refer also to guideline 5.
10.6 Allow the user to configure the user agent in named profiles that
may be shared (by other users or software). [Priority 2]
Users must be able to select from among available profiles or
no profile (i.e., the user agent default settings).
Techniques:
Configuration profiles allow individual users to save their
user agent settings and re-apply them easily. This is
particularly valuable in an environment where several people
may use the same machine. Profiles may include rendering
preferences as well as user email address, proxy information,
stylesheet preferences, etc.
The user should be able to easily transfer profiles between
installations of the same user agent. One way to facilitate
this is to follow applicable operating system conventions for
profiles.
Users should be able to switch rapidly between profiles (or the
default settings) and to set a new default profile. This is
helpful when:
+ Several people use the same machine.
+ One user is being helped by another who may not recognize the
information being displayed using the user's profile.
User agents may apply a profile when the user logs in. They may
also allow users to apply settings interactively, for example
by allowing them to choose from a list of named profiles in a
menu.
Sample profiles (based on common usage scenarios) can assist
users in the initial set up of the user agent. These profiles
can serve as models and may be copied and fine-tuned to meet an
individual's particular needs.
Cascading Style Sheets may be part of a source document or
linked externally. Stand-alone style sheets are useful for
implementing user profiles in public access computer
environments where several people use the same computer. User
profiles allow for convenient customization and may be shared
by a group.
A text profile may be pasted in email and is useful for
technical support purposes.
__________________________________________________________
10.7 Provide default input configurations for frequently performed
operations. [Priority 3]
Make the most frequently used commands easy to access. In
particular, provide convenient mappings to functionalities that
promote accessibility such as navigation of links.
Techniques:
+ Ask users with different disabilities and combinations of
disabilities to test your configurations.
+ Allow users to accomplish tasks through repeated keystrokes
(e.g., sequential navigation) since this means less physical
repositioning for all users.
+ However, repeated keystrokes may not be efficient for some
tasks. For instance, do not require the user to position the
pointing device by pressing the "down arrow" key repeatedly.
+ Input configurations should allow quick and direct access
that does not rely on graphical output. Do not require the
user to navigate through "space" (through a graphical user
interface) as the only way to activate a functionality.
__________________________________________________________
10.8 Allow the user to configure the graphical arrangement of user
interface controls. [Priority 3]
Techniques:
+ Allow multiple icon sizes (big, small, other sizes).
+ Allow the user to choose icons and/or text
+ Allow the user to change the grouping of icons
+ Allow the user to change the position of control bars, icons,
etc. Do not rely solely on drag-and-drop for reordering tool
bar; the user must be able to configure the user interface in
a device-independent manner (e.g., through a text-based
profile).
__________________________________________________________
Guideline 11. Provide accessible product documentation and help
Checkpoints for user interface accessibility:
11.1 Provide a version of the product documentation that conforms to
the Web Content Accessibility Guidelines. [Priority 1]
User agents may provide documentation in many formats, but at
least one must be accessible per the Web Content Accessibility
Guidelines [WAI-WEBCONTENT]. Alternative equivalents for
content, navigation mechanisms, and illustrations will all help
make the documentation accessible.
Techniques:
It is essential that any web-based support and/or documentation
that is produced or maintained by the manufacturer of a user
agent or by a sub-contractor of the user agent's developer,
conform to the Web Content Accessibility Guidelines
[WAI-WEBCONTENT]. This includes (but is not limited to):
1. text equivalents of all graphics
2. extended descriptions of screen-shots, flow-charts, etc.
3. clear and consistent navigation and search mechanisms
4. use of the NOFRAMES element when the support/documentation is
presented in a FRAMESET
5. serial listings of keystrokes and keybindings
Accessing documentation in familiar applications is
particularly important to users with disabilities who must
learn the functionalities of their tools and be able to
configure them for their needs. Commonly used applications are
also more likely to be compatible with assistive technology.
Electronic documentation should not be provided in proprietary
formats.
Where possible, allow users to download documentation in a
single block (e.g., single HTML file, zip archive of several
HTML and image files, etc.)
Run-time help and any Web-based help or support information, as
well as the documentation distributed with the tool, must be
fully accessible to persons with disabilities. Per checkpoint
1.1, the user must be able to invoke the run-time help with a
simple, well documented keystroke command. It is strongly
suggested that the keybinding used to invoke the UAs help
system be the default "Help" keybinding for the operating
system.
Users with print disabilities may need or desire documentation
in alternative formats such as Braille (refer to "Braille
Formats: Principles of Print to Braille Transcription 1997"
[BRAILLEFORMATS]), large print, or audio tape. User agent
manufacturers may provide user manuals in alternative formats.
Documents in alternative formats can be created by agencies
such as Recording for the Blind and Dyslexic and the National
Braille Press.
User instructions should be expressed in an input
device-independent manner. Provide instructions for using or
configuring the user agent in a manner that can be understood
by a user of any input device including a mouse or keyboard.
For example, "Select the Home button on the toolbar" or "Select
Home from the Go menu to return to the Home page."
Universal design means that access to features that help
accessibility should be integrated into standard menus. User
agents should avoid regrouping access to accessibility features
into specialized menus.
Proper documentation is important to developers with
disabilities, not just users with disabilities. A disabled user
may be a developer using the user agent as a test bed or
someone who needs critical information that can only be
obtained by as direct a path to the tool's mechanics and
"under-the-hood" features as possible. Detailed accessible
documentation (e.g., distributed on CD-ROM) is important to
allow assistive technology developers access to APIs, etc.
Ensure that product identification codes are accessible to
users so they may install their software. Codes printed on
product cases will not be accessible to people with visual
disabilities.
__________________________________________________________
11.2 Document all user agent features that promote accessibility.
[Priority 1]
For example, review the documentation or help system to ensure
that it discusses the functionalities addressed by the
checkpoints of this document.
Techniques:
Include references to accessibility features in these parts of
the documentation:
1. Indexes. Include terms related to product accessibility in
the documentation index (e.g., "accessibility", "disability"
or "disabilities").
2. Tables of Contents. Include terms related to product
accessibility in the documentation table of contents (e.g.,
features that promote accessibility)
3. Include instructions on how to modify all user configurable
defaults and preferences (e.g, images, video, style sheets,
and scripts) as specified by the documentation.
4. Include a list of all keyboard shortcuts or other input
configuration information in the accessibility section of the
documentation.
5. Document the features implemented to conform with these
Guidelines.
__________________________________________________________
11.3 Document the default input configuration (e.g., default keyboard
bindings). [Priority 1]
Techniques:
Here is a table showing mappings between Netscape Navigator
functions (or potential functions) and their keyboard shortcuts
in Macintosh, Unix, and Windows versions. If a function exists
in the browser but does not have a shortcut, its corresponding
cell is marked with an asterisk(*). If the function does not
exist, it is left blank. Note. This table lists some, but not
all, functionalities and keyboard shortcuts of Netscape
Navigator. It is meant to illustrate, not serve as definitive
documentation.
Some entries contain links to special notes. The number in
parentheses following the link is the number of the relevant
note.
Linear version of of Netscape Navigator Keyboard Shortcuts.
CAPTION: Netscape Navigator Keyboard Shortcuts
Function Macintosh (v 4.61) Unix (v 4.51) Windows (v 4.7)
Move within a document
Scroll to next page Page Down Page Down Page Down
Scroll to previous page Page Up Page Up Page Up
Scroll to top * * Ctrl-Home
Scroll to bottom * * Ctrl-End
Move between documents
Open a new document Command+L Alt+O Ctrl+O
Stop loading a document Command+. Esc Esc
Refresh a document Command+R Alt+R Ctrl+R
Load previous document Command+[
or
Command+Left Arrow Alt+Left Arrow Alt+Left Arrow
Load next document Command+]
or
Command+Right Arrow Alt+Right Arrow Alt+Right Arrow
Navigate elements within a document
Move focus to next frame * * *
Move focus to previous frame * * *
Move focus to next active element (1) Tab Tab Tab
Move focus to previous active element (1) Shift+Tab Shift+Tab
Shift+Tab
Find word in page Command+F Alt+F Ctrl+F
Act on HTML elements
Select a link * * Enter
Toggle a check box * * Shift or Enter
Activate radio button * * Shift
Move focus to next item in an option box * * Down Arrow or Right Arrow
Move focus to previous item in an option box * * Up Arrow or Left
Arrow
Select item in an option box * * Enter
Press a button (2) Return Enter Enter
Navigate menus
Activate menu * * Alt+ the underlined letter in the menu title
Deactivate menu * Esc Esc
Move focus to next menu item * * (3) Down Arrow
Move focus to previous menu item * * (3) Up Arrow
Select menu item * underlined letter in the menu item Enter
Move focus to submenu * * (3) Right Arrow
Move focus to main menu * * (3) Left Arrow
Navigate bookmarks
View bookmarks menu * (4) * Alt+C+B
Move focus to next item in bookmarks menu Down Arrow (4) * Down Arrow
Move focus to previous item in bookmarks menu Up Arrow (4) * Up Arrow
Select item in bookmarks menu Return (4) * Enter
Add bookmark Command+D Alt+K Ctrl+D
Edit bookmarks Command+B Alt+B Ctrl+B
Delete current bookmark (5) Delete Alt+D Delete
Navigate history list
View history list Command+H Alt+H Ctrl+H
Move focus to next item in history list * * Down Arrow
Move focus to previous item in history list * * Up Arrow
Move focus to first item in history list * * Left Arrow
Select item in history list * * Enter (6)
Close history list Command+W Alt+W Ctrl+W
Define view
Increase font size (7) Shift+Command+] Alt+] Ctrl+]
Decrease font size (7) Shift+Command+[ Alt+[ Ctrl+[
Change font color * * *
Change background color * * *
Turn off author-defined style sheets * * *
Turn on user-defined style sheets (8) ? ? ?
Apply next user-defined style sheet ? ? ?
Apply previous user-defined style sheet ? ? ?
Other functionalities
Access to documentation * * *
Notes.
1. In Windows, active elements can be links, text entry boxes,
buttons, checkboxes, radio buttons, etc. In Unix and
Macintosh, Tab cycles through text entry boxes only.
2. In Windows, this works for any button, since any button can
gain the focus using keyboard commands. In Unix and
Macintosh, this only applies to the "Submit" button following
a text entry.
3. In Unix, the menus can not be opened with shortcut keys.
However, once a menu is opened it stays opened until it is
explicitly closed, which means that the menus can still be
used with shortcut keys to some extent. Sometimes left and
right arrows move between menus and up and down arrows move
within menus, but this does not seem to work consistently,
even within a single session.
4. In Macintosh, you can not explicitly view the bookmarks menu.
However, if you choose "Edit Bookmarks", which does have a
keyboard shortcut, you can then navigate through the
bookmarks and open bookmarked documents in the current
window.
5. To delete a bookmark you must first choose "Edit Bookmarks"
and then move the focus to the bookmark you want to delete.
6. In Windows, when you open a link from the history menu using
Enter, the document opens in a new window.
7. All three systems have menu items (and corresponding shortcut
keys) meant to allow the user to change the font size.
However, the menu items are consistently inactive in both
Macintosh and Unix. The user seems to be able to actually
change the font sizes only in Windows.
8. It is important to allow users to set their own cascading
style sheets (css). Although Netscape does currently allow
the user to override the author's choice of foreground color,
background color, font, and font size, it does not allow some
of the advanced capabilities that make cascading style sheets
so powerful. For example, a blind user may want to save a
series of style sheets which show only headers, only links,
etc., and then view the same page using some or all of these
style sheets in order to orient himself to the contents and
organization of the page before reading any of the actual
content.
__________________________________________________________
11.4 In a dedicated section, document all features of the user agent
that promote accessibility. [Priority 2]
For example, list all pertinent features in a chapter entitled
"Accessibility Features". Note that this is a more specific
requirement than checkpoint 11.2.
Techniques:
When providing, in a dedicated section, documentation for all
features of the user agent that promote accessibility, it is
also essential that such information be clearly and obviously
linked to other sections of the documentation, where
appropriate. A dedicated section documenting the features of
the user agent that promote accessibility, however, must not be
the only method of documenting such features.
__________________________________________________________
_________________________________________________________________
3 Accessibility Topics
This section introduces some general techniques to promote
accessibility in user agent functionality. A list of assistive
technologies and browsers [USERAGENTS] designed for accessibility is
available at the WAI Web site.
3.1 Access to content
Users must have access to document content, however they are browsing.
Content can come from:
* the document source, both primary content and alternative
equivalents. Document source includes element content, attribute
values, and referenced content (e.g., images).
* style sheets.
* the user agent.
The most basic way to give users access to content is to render the
entire document in one stream, whether it be a two-dimensional
graphical layout, audio stream, or line-by-line Braille stream).
However, user agents should do much more to ensure that users can
understand a page by:
* Preserving structure when rendering
* Allowing the user to select specific content and query its
structure or context
* Allowing access to alternative equivalents of content.
* Using and generating metadata to provide context
* Allowing the user to configure the user agent for different
rendering options
These topics are addressed below.
3.1.1 Preserve and provide structure
Retain structure when rendering. For example, a graphical rendering of
tables conveys relationships among cells. Serial renderings (e.g., to
speech) must also make those relationships apparent, otherwise users
will not know where a table cell ends, or a list item, etc. One
technique for maintaining structure is to precede content with
"header" information (upon user demand). For example, give the
position of a table cell or it's associated headers. Or indicate the
position of a list item within nested lists.
Provide "intelligent" structure that may not be exactly what the DTD
says. For instance, in HTML, header elements do not nest, but
presenting the document as hierarchical may give users a better sense
of document structure. Use common idioms where known, even if they are
not expressly in the DTD.
3.1.2 Allow access to selected content
In the Amaya browser [AMAYA], users may access attribute values as
follows: Place the cursor at the element in question, open/swap to the
structure view. You are shown list of attributes and values. Another
technique: select the element (press escape in Linux), then the
attributes are all available from the attributes menu. For "alt", one
can also look at the alternate view, which renders text equivalents
instead of images - a lynx-like view. All the views are synchronized
for navigation (and for editing).
Users may want to select content based on the rendering structure
alone (i.e., that amounts to selecting across element borders).
Users may want to select content based on structure (e.g., a table
cell). Amaya allows users to "climb" the document tree by positioning
the cursor and pressing the Escape key. Each Escape selects one node
higher in the document tree, up to the root.
3.1.3 Access to alternative equivalents of content
Speech-based user agents providing accessible solutions for images
should, by default, provide no information about images for which the
author has provided no text equivalent. The reason for this is that
the image will clutter the user's view with unusable information
adding to the confusion. In the case of an speech rendering, nothing
should be spoken for the image element. This user should be able to
turn off this option to find out what images were inaccessible so that
the content author could be contacted to correct the problem.
In the case of videos, an assistive technology should, by default,
notify the user that a video exists as this will likely result in the
launch of a plug-in. In the case of a video, user agents should
indicate what type of video it is, accompanied by any associated
alternative equivalent. User agents should prefer plug-ins that
support system-specific accessibility features over those that don't.
In the case of applets, an assistive technology should, by default,
notify the user that an applet exists, as this will likely result in
the launch of an associated plug-in or browser specific Java Virtual
Machine. In the case of an applet, the notification should include any
associated alternative equivalents. This is especially important since
applets typically do provide an application frame that would provide
application title information.
When an applet is loaded, it should support the Java system
conventions for loading an assistive technology (refer to the appendix
on loading assistive technologies for DOM access). When the applet
receives focus, the browser user agent should first notify the user
about the applet as described in the previous paragraph and turn
control over to the assistive technology that provides access to the
Java applet.
Suppose an object with a preferred geometry is specified and not
rendered, should the alternative equivalent be rendered in the
preferred (but empty) region? What if the alternative equivalent
exceeds the size of the preferred geometry? One option is to allow the
user to specify through the UI whether to respect the preferred
geometries or ignore them.
3.1.4 Context
In addition to providing information about content, user agents must
provide contextual information. For example:
* table cell row/column position
* table cell header information.
* Nested list item numbers
* Content language
User agents can use style sheet languages such as CSS 2 [CSS2] and
XSLT [XSLT] to generate contextual information.
3.2 User control of style
To ensure accessibility, users must have final control over certain
renderings.
* For changing text size, allow font size changes or provide a zoom
mechanism.
* To hide content, use the CSS 'display' and 'visibility' properties
([CSS2], sections 9.2.5 and 11.2, respectively).
Implement CSS ([CSS1], [CSS2]) including the CSS 2 cascade order
(section 6.4.1) and user style sheets. The CSS 2 cascade order ensures
that user style sheets with "!important" (section 6.4.2) take
precedence over author styles, giving users final control. Style
sheets give authors design flexibility while offering users final
control over presentation (refer also to Web Content Accessibility
Guidelines 1.0 checkpoint 3.3 ([WAI-WEBCONTENT]). CSS should be
implemented by user agents that implement CSS for text that it
renders. CSS includes properties for audio, Braille (fixed and
refreshable), screen, and print rendering, and all relevant properties
for supported output media should be implemented.
Note that in the CSS cascade order, markup is given less weight than
style sheet rules. Thus, an author may use both presentation markup
and style sheets, and user agents that support style sheets will
prefer the latter.
A user style sheet can be implemented through a user interface, which
means that the user may not have to understand how to write style
sheets; they are generated or the user agent acts as though they were.
For an example of this, refer to the style sheets implementation of
Amaya [AMAYA], which provides a GUI-based interface to create and
apply internal style sheets. The same technique could be used to
control a user style sheet.
For images, applets, and animations:
Background images may be controlled by the use of local style sheets,
and more effectively if these can be dynamically updated. Animation
rate depends on the players used. User agents that provide native
rendering of animation (for example a movie player, a driver for
animated GIF images, or a java machine) should enable the control of
animation rates, or at least allow the user to stop, and to play
frame-by-frame, as well as straight rendering. A user agent could
provide control of the general timing of a presentation, combined with
the ability to select from available tracks manually. An issue to bear
in mind is that when animation is synchronized with audio, a user may
need the ability to play the animation separately from the associated
audio.
For time-based presentations:
Implement user controls to start, atop, rewind and pause
presentations, and where multiple tracks are supported, to choose
which tracks should be rendered. SMIL 1.0 [SMIL] provides for a number
of these features. A SMIL implementation should provide for direct
user control, as well as activation of the controls through a
published API, for developers of assistive technologies.
For user agents rendering audio:
On selecting from among available description tracks. SMIL 1.0 [SMIL]
allows users to specify captions in different languages. By setting
language preferences in the SMIL player, users may access captions (or
audio) in different languages.
The G2 player from Real Networks currently allows users to specify
which language they prefer, which can be evaluated in a SMIL document
to choose from among text or audio tracks. Currently only one language
can be indicated which does not permit choosing, for example, English
spoken audio with Spanish captions.
The Quicktime player currently permits turning on and off any number
of tracks individually, which can include audio, video, and text.
For user agents rendering video:
Implement the CSS positioning and/or SMIL layout languages. Allow the
user to freeze a presentation, manually move and resize component
visual tracks (including captions, subtitles and signed translations)
and to apply CSS stylesheets to text-based presentation and SVG.
For user agents rendering speech:
CSS 2 aural style sheet properties ([CSS2], section 19) can allow
users to control speech rate, volume, and pitch. These can be
implemented by allowing the user to write and apply a local style
sheet, or can be automatically generated by means of (accessible) user
controls, which should also be controllable through an API.
User interface:
* Allow the user to select large or small buttons and controls (and
ensure that these values are applied consistently across the user
interface)
* Allow the user to control features such as menu font sizes, or
speech rates - this may be achieved through use of operating
system standards.
* Allow the user to regroup buttons and controls, and reorder menus.
3.3 Link techniques
* Address broken link handling so that it doesn't disorient users.
For example, leave viewport as is and notify user.
* Provide the user with media-independent information about the
status of a link as the link is chosen. For example, do not rely
solely on font styles or color changes to alert the user whether
or not the link has previously been followed. The user should be
able to pick from amongst a list of alert mechanisms (i.e. color
changes, sound clips, status line messages, etc.), and should not
be limited to only one type of alert mechanism.
+ For assistive technologies: Provide the user with the option
to have the "title" (if present) or the hyperlink text made
available to the user when the user navigates from link to
link.
* Alert the user if following a link involves the payment of a fee.
* When presenting the user with a list of the hyperlinks contained
in a document, allow the user to choose between "Display links
using hyperlink text" or "Display links by title (if present)",
with an option to toggle between the two views. For a link without
a title, use the link text.
+ Provide the user with orientation information about the
listed links. For example, identify a selected link as "Link
X of Y", where "Y" is the total number of links available in
the document.
* Offer the user a list of links which have been visited and a list
of links which have not yet been visited, or provide a
media-independent mechanism to distinguish between visited and
unvisited links. Do _not_ rely on visual or aural prompts alone to
signify the difference between visited and unvisited links.
* Offer the user a list of links which are internal (i.e., local to
document) and those which are external, or provide a
media-independent mechanism to distinguish between external and
internal links in a list of links. Do not rely on visual or aural
prompts *alone* to signify the difference between internal and
external links.
* Use the CSS2 ':before' pseudo-elements ([CSS2], section 5.12.3) to
clearly indicate that something is a link (e.g., 'A:before {
content : "LINK:" }').
* Implement the CSS pseudo-class ':hover'.
Lynx allows the user to choose from the following options for images
without "alt" supplied:
* Insert a generic placeholder (e.g., [IMAGE]) in place of the
image.
* Insert the file name in place of the image.
* Render nothing.
The same technique might be used when "alt" is supplied but whitespace
only. However, if an image with empty or whitespace "alt" text is part
of a link:
* Insert a generic placeholder (e.g., [LINK]) in place of the image.
* If supplied for the link element, render the "title" attribute.
* Otherwise, if the link designates an HTML document, use the
content of the TITLE element in that document as link text.
* Otherwise render the filename or URI of the designated resource.
Lynx [LYNX] numbers each link and other element and provides
information about the relative position of the section of the
document. Position is relative to the current page and the number of
the current page out of all pages. Each page usually has 24 lines.
Information about link status and other properties can be provided in
an information view such as that provided by Netscape Navigator about
how many and what types of elements are in a document.
User agents should not consider that all local links (to anchors in
the same page) have been visited when the page has been visited.
User agents may use graphical or aural icons to indicate visited links
or broken links.
Users should be able to:
* Configure what information about links they wish presented to
them.
* Turn on and off automatic rendering of this information when a
link is focused.
* Get information about a focused link on demand, even if automatic
rendering has been turned off.
3.4 List techniques
Ordered lists help non-visual users navigate. Non-visual users may
"get lost" in lists, especially in nested lists and those that do not
indicate the specific nest level for each list item. Until user agents
provide a means to identify list context clearly (e.g., by supporting
the ':before' pseudo-element in CSS2), content developers should
include contextual clues in their lists.
For numbered lists, compound numbers (or letters, numbers, etc.) are
more informative than simple numbers. Thus, a list numbered "1, 1.1,
1.2, 1.2.1, 1.3, 2, 2.1," provides more context than the same list
without compound numbers, which might be formatted as follows:
1.
1.
2.
1.
3.
2.
1.
and would be spoken as "1, 1, 2, 1, 2, 3, 2, 1", conveying no
information about list depth.
CSS ([CSS1], [CSS2]) allow users to control number styles (for all
list, not just ordered) through user style sheets.
Example.
The following CSS 2 style sheet (taken from CSS 2, section 12.5) shows
how to specify compound numbers for nested lists created with either
UL or OL elements. Items are numbered as "1", "1.1", "1.1.1", etc.
End example.
Even without CSS, user agents may allow users to turn on and off
contextual rendering of nested lists.
3.5 Table techniques
Tables were designed to structure relationships among data. In
graphical media, tables are often rendered on a two-dimensional grid,
but this is just one possible interpretation of the data. On the Web,
the HTML TABLE element has been used more often than not to achieve a
formatting effect ("layout tables") rather than as a way to structure
true tabular data ("data tables").
Layout tables cause problems for some screen readers and when
rendered, confuse users. Even data tables can be difficult to
understand for users that browse in essentially one dimension, i.e.
for whom tables are rendered serially. The content of any table cell
that visually wraps onto more than one line can be a problem. If only
one cell has content that wraps, there is less problem if it is in the
last column. Large tables pose particular problems since remembering
cell position and header information becomes more difficult as the
table grows.
User agents facilitate browsing by providing access to specific table
cells and their associated header information. How headers are
associated with table cells is markup language-dependent.
Tabular navigation is required by people with visual disabilities and
some types of learning disabilities to determine the content of a
particular cell and spatial relationships between cells (which may
convey information). If table navigation is not available users with
some types of visual disabilities and learning disabilities may not be
able to understand the purpose of a table or table cell.
3.5.1 Table rendering
A linear view of tables -- cells presented row by row or column by
column -- can be useful, but generally only for simple tables. Where
more complex structures are designed, allowing for the reading of a
whole column from header downward is important as is carrying the
ability to perceive which header belongs to which column or group of
columns if more than one is spanned by that header. It is important
for whole cells to be made available as chunks of data in a logical
form. It might be that a header spans several cells so the header
associated with that cell is part of the document chunk for that and
each of the other cells spanned by that header. Inside the cell, order
is important. It must be possible to understand what the relationships
of the items in a cell are to each other.
Properly constructed data tables generally have distinct TH head cells
and TD data cells. The TD cell content gains implicit identification
from TH cells in the same column and/or row.
For layout tables, a user agent can assist the reader by indicating
that no relationships among cells should be expected. Authors should
not use TH cells just for their formatting purpose in layout tables,
as those TH cells imply that some TD cells should gain meaning from
the TH cell content.
When a table is "read" from the screen, the contents of multiline
cells may become intermingled. For example, consider the following
table:
This is the top left cell This is the top right cell
of the table. of the table.
This is the bottom left This is the bottom right
cell of the table. cell of the table.
If read directly from the screen, this table might be rendered as
"This is the top left cell This is the top right cell", which would be
confusing to the user.
A user agent should provide a means of determining the contents of
cells as discrete from neighboring cells, regardless of the size and
formatting of the cells. This information is made available through
the DOM [DOM1]).
3.5.2 Cell rendering
Non-graphical rendering of information by a browser or an assistive
technology working through a browser will generally not render more
than a single cell, or a few adjacent cells at a time. Because of
this, the location of a cell of interest within a large table may be
difficult to determine for the users of non-graphical rendering.
In order to provide equivalent access to these users, compliant
browsers should provide a means of determining the row and column
coordinates of the cell having the selection via input (e.g.,
keyboard) commands. Additionally, to allow the user of a non-graphical
rendering technology to return to a cell, the browser should allow a
means of moving the selection to a cell based on its row and column
coordinates.
At the time the user enters a table, or while the selection is located
within a table, the user agent should allow an assistive technology to
provide information to the user regarding the dimensions (in rows and
columns) of the table. This information, in combination with the
summary, title, and caption, can allow the user with a disability to
quickly decide whether to explore the table of skip over it.
Dimensions is an appropriate term, though dimensions needn't be
constants. For example a table description could read: "4 columns for
4 rows with 2 header rows. In those 2 header rows the first two
columns have "colspan=2". The last two columns have a common header
and two subheads. The first column, after the first two rows, contains
the row headers.
Some parts of a table may have 2 dimensions, others three, others
four, etc. Dimensionality higher than 2 are projected onto 2 in a
table presentation.
The contents of a cell in a data table are generally only
comprehensible in context (i.e., with associated header information,
row/column position, neighboring cell information etc.). User agents
provide users with header information and other contextual
information. Techniques for rendering cells include:
* Provide this information through an API.
* Render cells as blocks. This may assist some screen readers. Using
this strategy, the user agent might render individual cells with
the relevant top and side headers attached.
* Allow navigation and querying of cell/header information. When the
selection is on an individual cell, the user would be able to use
a keyboard command to receive the top and left header information
for that cell. The user agent should appropriately account for
headers that span multiple cells.
* Allow users to read one table column or row at a time, which may
help them identify headers.
* Ignore table markup entirely. This may assist some screen readers.
However, for anything more than simple tables, this technique may
lead to confusion.
3.5.3 Cell header algorithm
User agents should use the HTML 4.0 algorithm to calculate header
information ([HTML40], section 11.4.3).
Since not all tables are designed with the header information, user
agents should provide, as an option, a "best guess" of the header
information for a cell. Note that data tables may be organized
top-to-bottom, bottom-to-top, right-to-left, and left-to-right, so
user agents should consider all edge rows when seeking header
information.
Some repair strategies for finding header information include:
* Consider that the top or bottom row to contains header
information.
* Consider that the leftmost or rightmost column in a column group
contains header information.
* If cells in an edge row or column span more than one row or
column, consider the following row or column to contain header
information as well.
The user may choose the form and amount of this information, possibly
announcing the row heads only once and then the column head or its
abbreviation ("abbr") to announce the cell content.
Issues to consider:
1. TH cells on both the left and right of the table need to be
considered.
2. For TH cells with "rowspan" set: the content of those TH cells
must be considered for each of the N-1 rows below the one
containing that TH content.
3. An internal TH in a row surrounded on either side by TDs has no
means to specify to which (row or column) that TH overrides what
existed to its left or above it.
4. Finding column header cells assumes they are all above the TD cell
to which they apply.
5. A TH with "colspan" set needs to be included in the list of TH for
the M-1 columns to the right of the column in which the TH is
found.
If the user agent is taking a guess at header information, the user
agent might find two or more possibilities. Provide the user with a
mechanism to review the possible choices and make a selection.
3.5.4 Table metadata
Users of screen readers or other serial access devices cannot easily
glean information about a page "at a glance". This is particularly
difficult when accessing two-dimensional tables and trying to
determine their content. Therefore, contextual information about
tables (available from author-supplied markup or generated by the user
agent) is very important to making them accessible.
Text metadata about tables can come from a number of elements,
attributes, the structure of the table itself, or other sources.
Useful information to make available to users includes:
* The number of column groups and columns.
* The number of row groups and rows, in particular information about
table headers and footers.
* Which rows contain header information (whether at the top or
bottom of the table).
* Which columns contain header information (whether at the left or
right of the table).
* Whether there are subheads.
* How many rows or columns a header spans.
* The row/column dimensions of the table.
The user should be able to get table summary information from inside a
cell. It might be helpful to provide two types of table summary
information, i.e. a brief summary and a more detailed summary.
3.5.5 Table navigation
All users should be able to determine quickly the nature and purpose
of a table. Examining the table visually often conveys a sense of the
table contents with a quick scan of the cells. Users with blindness or
low vision, users who have difficulty translating printed material, or
users in an eyes-busy or speech-based environment may not able to do
this. Table summary information can convey the nature of a table; in
HTML, summary information for tables comes from the "summary"
attribute on the TABLE element as well as the CAPTION element.
An auditory rendering agent, when the point-of-regard moves to a
table, might say, "Table: Tax tables for 1998," thus identifying the
nature of the table. The user could then use keyboard commands to move
the selection to the next logical block of information, or use a
different command to "burrow" into the table.
The "burrow" command should have an opposite "up" command, which would
move the selection from an individual cell to the table as a whole, so
that the user can leave a table from any cell within it, rather than
navigating to the end.
If the user moves the focus up to look over the summary information,
it should be possible to burrow back to the same cell.
When navigating a table that contains another table, this strategy can
avoid confusion. For example, if each row of a table contained five
cells, but the second row contained a 4x4 table in the third cell, a
user could be disoriented when the row did not end as expected.
However, when the selection moved to the third cell of the table, a
compliant browser would report that this was a table, and describe its
contents. The user would have the option of navigating to the fourth
cell of the parent table, or burrowing into the table within this
cell.
When rendering tabular information, the fact that it is tabular
information should be apparent. For a graphical user agent, such
information is commonly made obvious by the border attribute or by
visually apparent aligned white space between columns. However, for a
non-graphical agent, such information must also be made evident.
As the user agent shifts the selection to a table, it should first
allow users to access summary information about the table (e.g., the
CAPTION element or the "summary" attribute in HTML). Access to this
information allows the user to determine whether or not to examine the
contents of the table, or to move the selection to the next block of
content. Users should be able to choose not to have the summary
information presented, if, for example, they visit a table frequently
and don't want to hear the summary information repeated each time.
In many data tables, the meaning of the contents of a cell are related
to the contents of adjacent cells. For example, in a table of sales
figures, the sales for the current quarter might be best understood in
relation to the sales for the previous quarter, located in the
adjacent cell.
In order to provide access to contextual information for individuals
using non-graphical browsers, or for individuals with certain types of
learning disabilities, it is necessary for the user agent to allow the
selection to be moved from cell to cell, both right/left and up/down
via keyboard commands. The UA should inform the user when navigation
has led to a table edge.
The most direct method of performing such navigation would be via the
cursor keys, though other navigation strategies might be used.
Users of graphical browsers can easily locate cells within a table
that are at the intersection of a row and column of interest. To
provide equivalent access to users of non-graphical browsers,
equivalent means of navigation should be provided. The search function
of a browser will allow the user to locate key terms within a table,
but will not allow the user to find cells that are at the intersection
of rows and columns of interest.
A rich set of navigation functions could include:
* jump to specific cell
* up/down 1 or more rows
* left/right 1 or more columns
* bottom row in same column
* right column in same row
* jump to row headers for cell
* jump to column headers for cell
* jump back to cell
In some tables, cells may span more than one row or column and this
affects navigation techniques. For example, if you navigate up into a
cell which spans three columns, which cell above the span cell should
you go into if you go up another cell? Or what happens if you are in
the last cell of a row and the previous row has fewer columns?
3.5.6 Table search techniques
* An advanced search mode might provide entries for header
information, allowing the user to find information at the
intersection of columns and rows using the key terms.
* A search mode might allow the user to search for key terms that
are related to key header terms, allowing searches to be
restricted to specific rows or headers within a table.
The header information visible in a TH cell may be abbreviated, in
which case it should be user preference to see the "abbr" value if any
or the full contents.
Axis information may also help the user search into confined portions
of the table.
Column groups and row groups are other confining partitions of a table
in which a search may be limited.
Software:
* Table navigation script from the Trace Center
3.6 Frame techniques
Frames were originally designed for use by graphical user interfaces
to allow the graphical viewport to be broken up into pieces that could
change independently (e.g,. selecting an entry in a table of contents
in one frame changes the contents of a second frame). However Frames
can pose problems users who rely on synthesized speech, refreshable
Braille, and magnified views. The ability to access frame alternatives
is also important for some users with cognitive disabilities. Problems
include:
* Orientation: What frame am I in? How is the frameset organized?
What is the relationship among frames? What happens in frame B
when I select a link in frame A?
* Navigation: How do I get from frame to frame?
To help users, user agents should:
* Consider the author's alternative presentation to frames (e.g.,
provided by the HTML 4.0 NOFRAMES element ([HTML40], section
16.4.1).
* Inform the user that they are viewing a frameset.
* Provide information about the number of frames in the frameset.
* Provide (possibly nested) lists of links to each frame in the
frameset. The link text can be the frame title (given by "title"
or "name" if "title" is not present). Or, if no title or name are
available, render the title (e.g., the HTML TITLE element
[HTML40], section 7.4.2) of the document that is loaded into the
frame. Other alternative renderings for a frameset include simply
rendering each frame in the frameset sequentially as a block
(e.g., aligned vertically in a graphical environment).
* Highlight the current frameset (e.g., with a thick border, by
displaying the name of the current frameset in the status bar,
etc.
* Provide information about the current frame. Make available frame
title for speech synthesizers and Braille devices.
* If a page does not have a list of links within a frame available
outside the frame, make the list available outside the frame.
* Allow navigation between frames (forward and backward through the
nested structure, return to global list of links to frames). Note.
Recall that the user must be able to navigate frames through all
supported input devices.
* Allow navigation to alternative equivalents.
* Allow the user to bookmark the current frame.
* Inform the user if an action in one frame causes the content of
another frame to change. Allow the user to navigate quickly to the
frame(s) that changed.
To name frames in HTML, use:
1. The "title" attribute on FRAME, or if not present,
2. The "name" attribute on FRAME, or if not present,
3. Title information of the referenced frame source (e.g., the TITLE
element of the source HTML document), or
4. Title information of the referenced long description (e.g., what
"longdesc" refers to in HTML), or
5. Frame context (e.g., "Frame 2.1.3" to indicate the path to this
frame in nested framesets).
Users may also use information about the number of images and words in
the frame to guess the purpose of the frame. For example, few images
and few words is probably a title, more words is probably an index,
many words is probably text area.
Frame structure information should be available through the DOM and
appropriate accessibility interfaces. Using DOM and operating specific
accessibility API to expose frame information provides one means for
assistive technologies to provide alternative control of frames and
rendering of frame information. The user agent should fully implement
the DOM Level 1 Recommendation [DOM1] API related to frames:
HTMLFrameSetElement, HTMLFrameElement, and HTMLIFrameElement.
For people with visual disabilities who enlarge text on the screen to
improve readability, frames become distorted and unusable. Other users
with cognitive disabilities sometimes become disoriented in complex
side-by-side frame configurations. To improve access to frames, user
agents should allow frames to be viewed as a list so the user can
identify the number of frames and the functions of each frame. If
NOFRAMES information is present it should also be rendered so the user
can optionally use that view of the information.
Consider renderings of the following document:
Time Value of Money
The following illustrate how some user agents handle this frameset.
First, rendering in Microsoft Internet Explorer 5.0 on a Windows
platform:
Image shows the example frameset with five frame panes rendered in
Microsoft Internet Explorer 5.0
Rendering by Lynx on Linux:
Time Value of Money
FRAME: Size buttons
FRAME: Presentation Outline
FRAME: Navigation buttons
FRAME: Slide Image
FRAME: Notes
List of Presentation Slides
1. Time Value of Money
2. Topic Overview
3. Terms and Short Hand
4. Future Value of a Single CF
5. Example 1: FV example:The NBA's new Larry Bird exception
6. FV Example: NBA's Larry Bird Exception (cont.)
7. SuperStar's Contract Breakdown
8. Present Value of a Single Cash Flow
9. Example 2: Paying Jr, and A-Rod
10. Example 3: Finding Rate of Return or Interest Rate
11. Annuities
12. FV of Annuities
13. PV of Annuities
14. Example 4: Invest Early in an IRA
15. Example 4 Solution
16. Example 5: Lotto Fever
17. Uneven Cash Flows: Example 6:Fun with the CF function
18. Example 6 CF worksheet inputs
19. CF inputs continued
20. Non-Annual Interest Compounding
21. Example 7: What rate are you really paying?
22. Nominal to EAR Calculator
23. Continuous Interest Compounding
24. FV and PV with non-annual interest compounding
25. Non-annual annuities
26. Example 8: Finding Monthly Mortgage Payment
27. solution to Example 8
Graphical rendering by Home Page Reader on Windows:
Image shows the example frameset with five links for each of the frame
elements in IBM home page reader
Audio rendering by Home Page Reader on Windows: @@add here?@@
User agents may also indicate the number of frames in a document and
which frame is the current frame via the menu bar or popup menus.
Users can configure the user agent to include a FRAMES menu item in
their menu bar. The menu bar makes the information highly visible to
all users and is very accessible to assistive technologies. In the
following snapshot, the menu bar indicates the number of frames and a
check next to the name of the frame element indicates which is the
current frame:
Image shows a pull down menu indicating the number of frames in a
document, the labels associated with each frame, and a check mark to
indicate the current frame
3.7 Form techniques
For labels explicitly associated with form controls (e.g., "for"
attribute on LABEL in HTML), make available label information when the
user is navigating among the form controls. This information must be
provided in a device-independent manner, and the user should be able
to choose from a list of mechanisms that provide access to the content
of the label.
For semantic information explicitly associated with groupings of form
controls (e.g., groupings of radio buttons or checkboxes contained in
a FIELDSET), make available the information contained in the LEGEND
defined for the FIELDSET to the user. This information must be
provided in a device-independent manner, and the user should be able
to choose from a list of mechanisms that provide access to the content
of the LEGEND.
Provide information about the percentage of form that has already been
filled out as the user moves through the form controls. This
information must be provided in a device-independent manner. The user
should also be able to query the user agent through a simple,
well-documented mechanism (such as a keystroke or keystroke
combination) to learn what percentage of the form has been completed.
Allow the user to know what percentage of a form has been completed as
the user navigates the form. will help users avoid prematurely
submitting an incomplete form. This is particularly important for
anyone moving through a form sequentially; users who encounter a
submit button usually think this means the end of a form, but it may
not be. (Refer also to the technique detailing methods of providing
users with orientation information about individual form controls when
a form control receives focus for a more detailed discussion of this
issue.)
Provide the user with orientation information about a form. Users
should be able to query the user agent for:
* the presence of a form -- the user should be able to query to user
agent for the presence of a form within the document being
rendered. Some user agents (such as Opera and Netscape Navigator)
already indirectly provide such functionality in a non-interactive
manner, through the provision of "form navigation" keyboard
commands. When invoked, these "form navigation" commands move the
user agent's focus to the first form field contained in the
document currently being rendered (provided, of course, that the
document contains a form. Although providing discrete "form
navigation" commands allows users to quickly move to the first
form field within a document, users need to be explicitly notified
if the document does not contain a form. Such notification should
be conveyed in a device-independent manner, and the user should
not be limited to one means of notification (i.e., display a
message on the status bar and play a sound).
* the number of forms in a document
Provide the user with orientation information about individual form
controls when a form control receives focus. For example, the most
basic orientation information would be to identify the form control
with focus as "Field X of Y", where "Y" is the total number of fields
contained in the form. This will help prevent users accessing the form
serially (such as a blind user using a screen reader or someone using
a voice browser over a phone) from prematurely invoking the form's
submit mechanism. It is a common practice for forms (particularly
those used to query search engines) to be laid out visually, so that
the submit and reset buttons (if present) immediately follow a
text-entry field, despite the presence of other form controls (such as
radio buttons and checkboxes) within the FORM element. A user
accessing such a form in a serial manner, therefore, is likely to
mistake the submit button for the end of the form, and activate it,
unaware that it is followed by further form controls which could -- in
the example of a search engine query submission form -- prove an
invaluable aid in tailoring the content being submitted via the form.
Use of such orientation information (i.e., "Field X of Y" or the
percentage of the form completed) will also decrease the amount of
time needed to submit the form (a crucial consideration when forms are
being used to facilitate bidding for online auctions) as well as
reduce the frustration of the end user, who, due to the visually
oriented layout of the form, is confused when the submission of the
form repeatedly leads to a message such as "Form Incomplete - Use your
browser's back button to return to the form".
When a document contains more than one form, form control orientation
information should also include data which will identify to which form
the form control with focus belongs. Notification could take the form:
Form Z: Field X of Y
where "Z" identifies the form, "X" the form field with focus an "Y"
the total number of form fields contained in "Form Z".
Provide more detailed orientation information pertaining to form:
* When a grouping of radio buttons receives focus, identify the
radio button with focus as "Radio Button X of Y", where "Y"
represents the total number of radio buttons in the grouping. HTML
4.0 HTML 4.0 specifies the FIELDSET element ([HTML40], section
17.10), which allows authors to group thematically related
controls and labels. The LEGEND element ([HTML40], section 17.10)
assigns a caption to a FIELDSET. If a LEGEND has been defined for
the grouping of radio boxes, use the information contained within
the LEGEND to more precisely identify the number of radio buttons
in the grouping. For example, if the LEGEND element has been used
to identify a FIELDSET of radio buttons, each of which has a LABEL
element ([HTML40], section 17.9.1) associated with it, as
"Connection Rate", identify the radio button as it receives focus
as "Connection Rate: Radio button X of Y: 28.8kpbs", where "Y"
represents the total number of radio buttons in the grouping and
"28.8kbps" is the information contained in the LABEL associated
with the radio button with focus.
* Provide information about what is required for each form control.
GUI browsers, for example, could convey such information via
context- sensitive help. Lynx conveys this information by
providing information about the currently selected form control
via a status line message:
+ (Radio Button) Use right-arrow or RETURN to toggle
+ (Checkbox Field) Use right-arrow or RETURN to toggle
+ (Option List) Hit return and use arrow keys and return to
select option
+ (Text Entry Field) Enter Text. Use UP or DOWN arrows or "tab"
to move off
+ (Textarea) Enter text. UP/DOWN arrows or "tab" to move off
(^Ve for editor) Note. The ^Ve (caret-V, e) command, included
in the TEXTAREA status line message, enables the user to
invoke an external editor defined in the local Lynx
configuration file (lynx.cfg). For more information, please
refer to the following technique.
Allow the user to invoke an external editor when a TEXTAREA receives
focus. A user may wish to use an external editor, rather than enter
text directly in a TEXTAREA for myriad reasons, including:
* the ability to more efficiently and expeditiously review the text
being input
* the ability to spell check the text being input
* the ability to use macros or other special features of the
external editor, including the ability to increase the contrast
between foreground and background colors, access to a wider range
of screen-display fonts, etc.
* the ability to save a local copy of the text being input
* the user's familiarity with the external editor will encourage the
user to actually enter text into a TEXTAREA--an exercise which is
often an extremely daunting task, given the limitations imposed by
the physical dimensions of the TEXTAREA. A user will also find it
much easier to review what he or she has typed when using an
external editor.
Provide information about the order of form controls (e.g., as
specified by "tabindex" in HTML). This is important since:
* most forms are visually oriented, employing changes in font size
and color
* users who access forms serially need to know they have supplied
all the necessary information before submitting the form.
Provide information about required fields. Since authors often use
color changes, font styling, or a graphical symbol alone to express
that a field is required, the user should be able to configure the
user agent so that it alerts him that the field is required for
submission of the form content. Strategies for achieving this include:
* Allow the user to view a list of required form fields. Such a list
should be invokable via a simple and well documented keybinding.
* Allow the user to define an alert mechanism (such as the playing
of a sound) which will be invoked when a required field receives
focus. The user should be able to pick from amongst a list of
alert mechanisms (i.e. color or font-style changes to the field
label, the playing of a sound clip, a status line message, etc.),
and should not be limited to only one type of alert mechanism. Do
not rely on visual or aural prompts alone to signify a required
form field.
Allow the user to configure the user agent so that SELECT form fields
which use the "multiple" attribute to allow the end user to select
more than one OPTION can be transformed into a list of checkboxes.
* Preserve the LABELs set for the OPTGROUP and each individual
OPTION, and re-associate them with the user agent generated
checkboxes. The LABEL defined for the OPTGROUP should be converted
into a LEGEND for the resultant FIELDSET, and each checkbox should
retain the LABEL defined for the corresponding OPTION.
* Note. Lynx automatically transforms SELECT form fields which use
the "multiple" attribute to allow the end user to select more than
one OPTION into checkboxes.
Allow the user to exit a menu without selecting any option. For
example, when navigating through OPTION's, have some key like the ESC
key ot exit the list of OPTION's without making a selection.
Allow the user to configure the user agent sot that SELECT form fields
can be transformed into a list of radio buttons.
* Any such transformation should retain the accessibility
information defined for the original form controls.
* Note. Lynx provides this functionality as a configurable option,
which can be changed on-the-fly while a page is being rendered. To
promote the comprehensibility of the transformed output for users
using screen-readers and refreshable Braille displays, Lynx places
each OPTION that it transforms into a radio button on a separate
line.
3.7.1 Form submission techniques
Users (notably users with blindness or any user unaccustomed to online
forms) do not want forms to be submitted without their consent, e.g.,
when submitted through scripts. In this case user agents should
request confirmation before submitting the form content. Nor do they
wish to be prompted before each form submission when they have
explicitly submitted the form (e.g., through the standard submit
button).
Inadvertently pressing the RETURN or ENTER key is quite a prevalent
phenomenon among users of every level of expertise - especially those
who often find it necessary to switch between user agents. Lynx, for
example, uses the ENTER key within FORMs as a means of exposing
drop-down (or pop-up, depending upon your point of view) SELECT menus.
Thus, when one encounters a SELECT menu using Lynx, one: exposes the
content of the menu by pressing the ENTER key, and then is able to
navigate between OPTIONs using the up and down arrows or via Lynx's
text-search feature. When one finds the appropriate OPTION, it is
selected by pressing ENTER, which causes the selected item to be
displayed in the SELECT menu listbox.
The problem posed by the default "submit on enter" feature of most GUI
browsers is not limited to the SELECT menu problem outlined above.
Lynx (as well as several other text-based browsers) uses the
ENTER/RETURN key as a means of toggling several FORM controls, such as
the selection of checkboxes and radio buttons.
Speech users may be frustrated and misdirected by the use of
javascript and event handler controlled pseudo-forms, wherein the user
is presented with a menu (in the form of a listbox in GUI browsers),
and is redirected to a different viewport upon selection of an OPTION.
The markup behind such pseudo-forms is a mix of javascript (in
particular the "function switchpage(select)" command) and HTML FORM
controls, which utilize HTML4's event handler script attributes (in
particular the "onchange" event handler attribute has been defined. An
example (gleaned from the document source for one Web site follows: